throw Statement


throw [exception]

exception: Optional. Any expression.

The throw statement can be used without an argument, but only if the throw statement is contained within a catch block. In that situation, the throw statement re-throws the error caught by the enclosing catch statement. When an argument is provided, the throw statement throws the value of exception.

The following example throws an error based on a passed-in value, then illustrates how that error is handled in a hierarchy of try...catch...finally statements:

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function TryCatchDemo(x){ try { try { if (x == 0) // Evalute argument. throw "x equals zero"; // Throw an error. else throw "x does not equal zero"; // Throw a different error. } catch(e) { // Handle "x=0" errors here. if (e == "x equals zero") // Check for a handled error. return(e + " handled locally."); // Return error message. else // Can't handle error here. throw e; // Rethrow the error for next } // error handler. } catch(e) { // Handle other errors here. return(e + " error handled higher up."); // Return error message. } } print(TryCatchDemo(0)+ "\n"); print(TryCatchDemo(1));

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Copy Code

function TryCatchDemo(x){
   try {
      try {
      if (x == 0)                            // Evalute argument.
         throw "x equals zero";              // Throw an error.
      else
         throw "x does not equal zero";      // Throw a different error.
      }
      catch(e) {                             // Handle "x=0" errors here.
         if (e == "x equals zero")           // Check for a handled error.
            return(e + " handled locally."); // Return error message.
         else                                // Can't handle error here.
            throw e;                         // Rethrow the error for next
      }                                      // error handler.
   }
   catch(e) {                                // Handle other errors here.
      return(e + " error handled higher up."); // Return error message.
   }
}
print(TryCatchDemo(0)+ "\n");
print(TryCatchDemo(1));

Version 5

Reference

try...catch...finally Statement
Error Object

Arguments

Remarks

Example

Requirements

See Also

Reference